Why? Why not. We open forms out of forms. We open reports out of forms. We open reports out of reports. So why we should not open forms out of reports. ;-)
To open a Report out of a Report we use srw.run_report.
I have looked at this srw-package but there is nothing like run_report...

It's a bit like saying, I can embed a video inside a word document, so why can't I open a word document from inside my video when I play it in media player, The answer is, that it was not designed to be like that.